package com.hrm.utils;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/checkCodeBy")
@SuppressWarnings("all") // 使用注解抑制警告信息
public class CheckCode extends HttpServlet {

	protected void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		// 服务器通知浏览器不要缓存
		response.setHeader("pragma", "no-cache");
		response.setHeader("cache-control", "no-cache");
		response.setHeader("expires", "0");

		// 在内存中创建一个长80，宽30的图片，默认黑色背景
		// 参数一：长
		// 参数二：宽
		// 参数三：颜色
		int width = 120;
		int height = 38;
		BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

		// 获取画笔
		Graphics g = image.getGraphics();
		// 设置画笔颜色为灰色
		g.setColor(Color.GRAY);
		// 填充图片
		g.fillRect(0, 0, width, height);

		// 产生4个随机验证码，12Ey
		String checkCode = getCheckCode();
		// 将验证码放入HttpSession中
		request.getSession().setAttribute("CHECKCODE", checkCode);

		// 设置画笔颜色为黄色
		g.setColor(Color.YELLOW);
		// 设置字体的小大
		g.setFont(new Font("宋体", Font.BOLD, 24));
		// 向图片上写入验证码
		g.drawString(checkCode, 15, 25);

		// 将内存中的图片输出到浏览器
		// 参数一：图片对象
		// 参数二：图片的格式，如PNG,JPG,GIF
		// 参数三：图片输出到哪里去
		ImageIO.write(image, "PNG", response.getOutputStream());
	}

	/**
	 * 产生4位随机字符串
	 */
	private String getCheckCode() {
		String base = "01QWERTYUIOPLKJHGFDSAZX456789CVBNMqwertyuioplkjhgfds23dazxcvbnm";
		int size = base.length();
		Random r = new Random();
		StringBuffer sb = new StringBuffer();
		for (int i = 1; i <= 4; i++) {
			// 产生0到size-1的随机值
			int index = r.nextInt(size);
			// 在base字符串中获取下标为index的字符
			char c = base.charAt(index);
			// 将c放入到StringBuffer中去
			sb.append(c);
		}
		return sb.toString();
	}

	protected void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}

}
